The present invention relates generally to radiation shielding, and more particularly to providing a chassis shielding system.
Electromagnetic interference (EMI) is an electrical noise that creates a disturbance, or an undesired response in electrical circuits, equipment, or systems. Many types of commercial electronic equipment, such as computers and transmitters are a source of electromagnetic emissions. Most sources primarily produce electromagnetic (E) field emissions. Most conductive materials have low impedance and therefore reflect most of the E field waves.
Electromagnetic compatibility (EMC) is the extent to which a piece of hardware will tolerate electrical interference from other equipment, in other words, the ability of a device or system to function without error in its intended electromagnetic environment. Potential sources of electromagnetic compatibility problems include radio transmitters, power lines, electronic circuits, electric motors, and just about anything that utilizes or can detect electromagnetic energy.
Electronic circuits, equipment, and systems which are sensitive to electromagnetic radiation must be shielded from sources in order to ensure proper performance. Furthermore, when equipment radiates electromagnetic radiation, the equipment must be isolated, or shielded in order to prevent degradation of the performance of surrounding equipment.
Computers are generally designed and constructed to provide for the installation of supplemental circuit cards that can be mounted in the computer in order to provide a number of different functional options. Supplemental circuit cards are typically designed and constructed with a standard mounting bracket attached to a circuit board. A typical computer has openings in the computer chassis to allow the installation of the supplemental circuit cards. However, the openings in the computer chassis increase the potential that unwanted radiation, such as electromagnetic and radio frequency emissions will have a deleterious impact upon the computer.
Shielding, which involves the use of materials to reduce radiation by reflection and/or absorption, is used in many different equipment environments, particularly those in which gaskets are required to seal seams and gaps in housings and door enclosures. Shielding is most effective when the shielding mechanism is suitably placed to cause an abrupt discontinuity in the path of radiation emissions. Additionally, shielding effectiveness and performance is a function of the properties and configuration of the shielding mechanism. Therefore, since one of the largest single sources of radiation emissions or electromagnetic leakage can occur along contact surfaces between two parts, in these situations, it is important to have a shield which is capable of establishing proper contact to ensure that a good conductive seal results.
In one conventional method, a device is designed with a multiplicity of precisely deflected xe2x80x9cfingerxe2x80x9d for providing contact between a circuit card bracket and a computer chassis. This design is very expensive device because the tooling used to manufacture the device is quite expensive. FIG. 1 is a top view of the conventional device 100 that utilizes a multiplicity of fingers 10 in the prior art. FIG. 2 is a side view of the conventional device 100 depicting how the multiplicity of fingers 10 are precisely deflected away from the sheet 20 of the device 100. FIG. 3 is a close up cross-sectional view of the precisely deflected finger 10. As shown in FIG. 3, Finger 10 has a bi-directional formation with a portion 10 that is deflected away from the sheet 20 in one direction, and a top end 14 which bends back towards the sheet 20 in the opposite direction. Significantly, FIG. 3 also shows the conspicuous deflection 16 which occurs when the finger 10 is formed out and away from the sheet 20. FIG. 4 is a close-up cross-sectional view illustrating the desired juxtaposition of the fingers of a conventional device when interposed between a circuit card 18 and a computer chassis 19. Apparent in FIG. 2, if the deflection 16 of fingers 10 is not properly and precisely deflected away from the sheet 20, proper contact between fingers 10 and computer chassis 19 is jeopardized. Therefore, this conventional device and method suffers from a number of shortcomings since circumstances which would cause the fingers to be pushed in too far, or not be deflected out far enough from the sheet will negatively impact the effectiveness of the device.
For example, the precise deflection of the finger contactors is not obtained during manufacturing, or when the precise deflection of the fingers is distorted once the device is used, the integrity of the conventional device becomes compromised, and the efficacy of the conventional device is jeopardized. As shown, the deflected finger contactors are suspended with minimum support from the main sheet of the device. Therefore, the fingers are vulnerable to distortion once the device has been wedged between two opposing surfaces for shielding. In this conventional device, since proper contact and effective shielding is contingent upon the precise deflection of the fingers, the conventional device would be rendered ineffective if the finger deflection is distorted.
Accordingly, what is needed is a chassis shielding system which is capable of shielding unwanted emissions. The system should utilize a shield which is structurally durable, and which effectively controls unwanted radiation in an interference condition. Further, the shield should be inexpensive to manufacture, and provide proper sealing. The present invention addresses such a need.
A computer chassis in accordance with the present invention is disclosed. The chassis includes a first body, a second body, and an electromagnetic shield coupled between the first and second bodies. The shield includes a plurality of dimples and a plurality of valleys for providing an electromechanical seal when the shield is placed in an interference condition.
Accordingly, the chassis shielding system and device in accordance with the present invention is capable of controlling unwanted radiation. The shielding system in accordance with the present invention overcomes the problems of conventional shielding designs and methods by utilizing a shield which is designed with a plurality of dimples and a plurality of valleys. Therefore, the sealing effect can be enhanced and unwanted radiation can be controlled in an interference condition. The improved shield creates an inner layer between two bodies and flexes to absorb the gap between the two bodies, thus creating a seal capable of preventing EMI from escaping from a unit. The present invention describes a durable, relatively inexpensive, and effective shield which is easier to manufacture, and which may be used in varying conditions.